Alkylation of paraffins



Jan. 7, 1947. F. E. #Rl-:Y 2,413,759

ALKYLAT ION OF PARAFFINS Filed Jan. 8, 1940 SNVEN. EJNI .LVNOILDVHJMOTOR FUEL.

SNVBW SNLLVBVdS ALKYL HALIDE RECYCLE HOLVWANIV ALKYL HALIDE PARAFFININVENTOR FREDERICK E FREY AT TORNEYS Patented Jan. 7, 1947 ALKYLATION FPARAFFIN S Frederick E. Frey, Bartlesville, Okla., assigner to PhillipsPetroleum Company, a corporation of Delaware I Application January8,1940, serial 10.312.964

This invention relates to the alkylation of parafiins, and moreparticularly to the alkylation of paraf'flns by alkyl halides.

I have found that alklation of paralns by alkyl halides may be effectedefficiently in the presence of concentrated sulfuric acid at ordinarytemperatures. -I have also found that sulfuric acid containing a lowconcentration of aluminum sulfate as a promoter is a good catalyst forsuch alkylations. I have further found that the alkylation reaction isfavored by the paraffin having a branched structure with a tertiaryhydrogen, and by the alkyl group being non-primary, that is, secondaryor tertiary. Furthermore, I have found that chlorides are somewhat moreadvantageous than other halides for the alkylation of parafiins.

11 claims. (cuzco-essa) An object of this invention is to effect thealkylation of parafns to form paramns having a higher molecular weight.

drawing, which shows a flow-diagram for a preferred mode of operationadapted to produce hydrocarbons boiling in the motor-fuel range.

A feed stock comprising chiefly Aat least one Y paraffin entersthesystem through inlet I having control-valve 2. Another feed stock,comprising chiefly at least one alkyl halide enters the system throughinlet 3 having control-valve 4.

tinuously or intermittently. The two feed stocks are intimately mixedwith each other and with concentrated sulfuric acid in alkylator 5, asby vigorous mechanical stirring. The sulfuric acid,

which enters alkylator 5 through inlet 6 having f control-valve 1, mayhave a strength within the range 90 to 105 per cent by weight,preferably between 96 and 102 per cent. Under the influence of thesulfuric acid, the paraflns are alkylated ,by the alkyl halide, formingless volatile paraiilns. The reaction temperature may be in the range 0to 125 F., preferably about 70 F.

Various reactions occur in alkylator 5, but the primary reaction isbelieved to be alkylation of paramns, especially isoparafilns, which arealkylated more easily than normal parafns. The

-Either or both feed stocks may be added conapproach completion.Generally a reaction time primary alkylation product appears to undergosecondary reactions that form lower-boiling and higher-boiling products;it doubtless also undergoes isomerization.

The reaction appears to proceed most efllciently for isoparaillns,especially those having four to eight carbon atoms per molecule,v andfor nonprimary alkyl halides in which the alkyl group has three to sixcarbonatoms. Of the non-primary alkyl halides, the tertiary reactsomewhat more rapidly than do the secondary; hence, if a secondary alkylhalide is used, it is advantageous to use a relatively high strength ofacid, such as to 105 per cent sulfuric acid.

Fluorides, chlorides, bromides, and iodides mayv be used, but bromidesand especially iodides have a marked tendency to reduce the sulfuricacid, and for this reason, and for economic reasons, it

is preferable to use the chlorides. The products formed when a propyl orbutyl chloride is reacted with isobutane or isopentane boil chiefly inthe gasoline range, are substantially completely saturated, and haveexcellent anti-knock ratings.

The reaction is favored by a high ratio' of paraffin to alkyl halide;for this reason the alkyl halide advantageously may be addedintermittently or portion-wise, as taught .for olens in l silversulfate, aluminum sulfate, and the like,l 4preferably in relatively lowconcentrations, such as from 0.5 to 5 per cent by weight.

Intimate contact between the sulfuric acid andv the alkylation reactantsis essential. This pref'- erably-is obtained by vigorous mechanicalstirring or mixingand by the vpresence of an adequate amount of acid. Italso may be promoted by the presence of certain emulsiilers in themixture, such as, for example, alkyl sulfates. As alkyl sulfates orequivalent compounds are formed to some extent during the reaction, asmall proportion of spent acid advantageously may be added to fresh acidto increase its ability to emulsify with the alkylation reactants.

Like all organic reactions, the alkylation of paramnswith alkyl halidesrequires some time to between 5 minutes and'3 hours is adequate; muchlonger periods preferably should be avoided, as

they favor secondary reactions that convert the aration of vadditionalyalkyl halide.

primary alkylation product into lower-boilingand higher-boilingproducts. Some indication of lthe progress of the reaction may beobtained from the rate of evolution of hydrogen halide, which is aLby-product ,of `the primary reaction; the hydrogen .halideadvantageously may be removed and used for the manufacture of additionalalkyl halide.

The sulfuric acid .may be withdrawn through valve n be subjected I-I andoutlet I2, and thence `itmay to a process of reclamation, if desired;or, alternatively, if may 4bereturned, partly or entirely, as is.desired yor .as trial indicates is desirable, to alkylator 5 throughvalve .I 3 and conduit Il. Hydrogen halide iswithdrawn through valveISand outlet I6,'and thence it'may be used for the prep- Thehydrocarbonssare passed vthrough valve I1 and conduit I8 yto alkali4treater I9, in which any acidicmaterial is removed by a treatment withan alkali, detailedequipment .for this being within the skill of 4oneversed in the art, and not shown. Under some conditions cf operation, asmall amount of .acidic material in the hydrocarbons .may be .tolerated;.undersuch conditions, if desired, at least 'part of the hydrocarbonmaterial from separating means I Il may be passed through valve 23 andconduits 24.1 and 2I directly to fractionating means 22without beingsubjected to an alkali treatment in alkali treater I9.

From alkali treater I9 the `hydrocarbons are passed through valve andconduit v2| to fractionating means 22. In fractionating means 22, thehydrocarbon material is fractionated into a heavy-oil fraction, which iswithdrawn through 4 andthe like, that is, hydrocarbons which contain atleast one tertiary hydrogen atom. Other examples oi! such hydrocarbonsare the isohexanes valve 125 and outlet 2B; into a gasoline or .motor-vfuel fraction, `which is withdrawn through valve 21 and outlet 28; .andvinto alight-hydrocarbon fraction, which may be rrecycled to `alkylatori through "valve .29 and'conduit '30, or may be discharged .from thesystem, entirely or in part, through valve 33 and outlet '34. Thislight-hydrocarbon fraction ,comprises chiefly unreacted paraiiins land,if desired when .used as .a recycle stock,the'lowerboiling alkylationproducts, such as those .containing kup to .about seven carbon atomspermolecule. If desired, .a light-gas irac-v ktion comprising chieflyparaillns having less than 'fourcarbon atoms per molecule, which arealkylated less readily than heavier hydrocarbons, may be withdrawnthrough valve 3| land outlet 32. Unreacted alkyl halides may be removedthrough conduit .35 and valve 36, `or may be recycled, entirely lor inpart, through conduit 31 and valve 38 toconduit 3.

It is to be understood, .in-connection with the foregoing process, thatonly the yprincipal steps have been shownrand that mechanical details ofeach step will be somewhat dependent on'each adaptation kof myinvention. The separating means and fractionating .meansshown willcomprise separators, fractionators, pumps, tanks, coole `ing andAheating units, etc., and similar equipment rwill also be required forthe other steps shown. Such equipment is of common knowledge, and

can bereadily included by one skilled in the art.

The `,term isoparafiln as used in 'this soecication, in.connection withthe charge'stock, refers to parain hydrocarbons such as isobutane 2-methylpropane), isopentane (2-methy1butane),

`2 and 3-,methylpentane, isoheptanes `such as 2- and 3-methylhexane,2,3- and 2,4-dimethylpentane, and `3-ethylpentane, and the like. Theisoparaillns produced generally, .although not necessarily always, willhave a similar structure.

When it is desired to produce a, gasoline, or some certain valuablehydrocarbon or hydrocarbons `boiling in the motor-fuel range, it willgenerally not be desirable to use an isoparafiin of higher molecularweight than isobutane or isopentane, or possibly an isohexane. When itis desired to produce .higher-molecular-weight paramns, correspondinglyhigher molecular weight initial paramns should be used as the chargestock.

It has been found that the more highly branched isoparamns of highermolecular weight are somewhat readily decomposed by prolonged contactwith sulfuric acid, and when these are used the reaction conditionsshould be so mediiled, as indicated by trial, that extensive deleteriousdecomposition does not take place. For this reason, it may at times bemore desirable to charge a simple isoparailln such as Z-methylheptane or2,4-dimethylhexane than la complex isoparamn such as2,2,4-trimethylpentane.

It will, of course, generally be impractical to charge any particularhydrocarbon in an Vabsolutely pure state, especially when usinghigherboiling hydrocarbons. When it is desired to produce particularindividual paramns in a relatively pure state, which can be readilypuried by fractional distillation, the hydrocarbon mixture chargedshould be relatively free of readily reactive parains other than theonenecessary to produce the desired product. When isoparafilns arereacted, the presence of limited amounts of normal parains is generallynot deleterious, and may at times be advantageous in controlling thereaction. At other times, less pure hydrocarbon fractions may be used.

As previously mentioned, it is preferable to use either ksecondary ortertiary alkyl halides, and it is also preferable that the halides bechlorides. The `alkyl halides having relatively lotv molecular weightsare generally readily obtained in a more or less pure form, especiallythose having not more than about six carbon atoms per molecule.Especially when it is desired to produce a gasoline, such as aviationgasoline, or some certain valuable hydrocarbon or hydrocarbons boilingin the motor-fuel range, it will be desirable to use such alow-molecular-weight halide in a pure state. In any case in which such aparticular hydrocarbon product is desired, the individual paramn andalkyl halide suitable for forming it may be readily selected by trial,in the light of the present disclosure. At other times, a more or lessimpure alkyl halide fraction may be used.

The temperature, reaction time, and relative amount of sulfuric acid areinterrelated. With higher temperatures and/or larger amounts of acid,shorter reaction times may be used. When it is desired to produce arelatively pure product, shorter reaction times and smaller yields perpass should be used, and when a .certain appreciable amount of sidereactions, or secondary reactions, may be tolerated. the process can beso operated as to have longer reaction times and higher yields per pass.The most desirable conditions in any particular instance can be readilydetermined by trial. When'sulfuric acid strength in excess of per centis mentioned, reference is made t0 anarco so-called "fuming sulfuricacid which. when titrated with an alkali, reacts with sufficient pose ofillustrating a few of the many possible modes of operation of theprocess; they `are not necessarily to be taken as establishinglimitations of the invention.

Example I To a mixture of 500 cc. of 96 per cent sulfuric acid and 359grams of isobutane in a flask, which was equipped with a refluxcondenser and a mercury-sealedmotor-driven stirrer and which was cooledto about F., was added 185 grams of tertiary butyl chloride during abouthalf an hour. The reaction mixture was stirred vigorously during theaddition and for about four hours thereafter; the temperature .was keptbelow about 40 F. Considerable hydrogen chloride was evolved.

On standing, the resultant mixture separated into an acid layer and intoa hydrocarbon layer, which was removed and washed with dilute alkali.This hydrocarbon layer was completely paraflinic and had a substantialcontent of hydrocarbons having more than four carbon atoms per molecule.

Example Il To a mixture of 500 cc. of sulfuric acid having a strength of102 per cent by weight and- 288 grams of isopentane, in a flask fittedwith a reux condenser and with a motor-driven stirrer, was added 160grams of isopropyl chloride during about half an hour. The reactionmixture was stirred vigorously during the addition and for about fourand a half hours thereafter; the temperature was maintained at about 70F. AfterI the acid was separated from the resultant mixture by settling,the hydrocarbon layer was freed from acidic material by washing withdilute alkali, and then it was fractionally distilled. The materialother than unreacted isopentane, and boiling from.85 to 410 F., amountedto 99 per cent by'weight of the total hydrocarbon product y and to 78percent by weight of the theoretical yield based on the formation ofoctane.

' Example m removed and freed from acidic material by washing withdilute alkali. 0f the hydrocarbon material other than isopentane, 96 percent by weight boiled between 85 and 410 F.; this fraction amounted lto83 per cent by weight of the theoretical yield based on the formation ofnonane.

`Example IV To a mixture of 500 cc. of sulfuric acid having a strengthof 102 per cent by weight and 288 grams of isopentane was added 185grams of secondary butyl chloride during about an hour. The mixture wasstirred vigorously during the addition and for about three hoursthereafter; the temperature was maintained at 68 F. The sulfuric acidwas separated by settling, and the hydrocarbon layer was freed fromacidic material by washing with alkali. Ofthe hydrocarbon material otherthan isopentane, 98 per cent by weight boiled between and 410 F.; thisfraction, which was completely parafilnic, amounted to per cent byweight of the theoretica1 yield based on the formation of nonane. i

Example V To a mixture of 180 grams of isopentane and 500 cc. ofsulfuric acid, which had a strength `.of 102 per cent lby weight andwhich contained 2 per cent by weight of aluminum chloride, was added 98grams of isopropyl chloride during about half an hour. 'I'he mixture wasstirred vigorously during the addition and for about four hoursthereafter; the temperature was maintained at 68 F. 'I'he sulfuric acidwas separated by settling; and the hydrocarbon layer was washed withdilute alkali. Of the hydrocarbon material other than isopentane, 98 percent by weight boiled between 85 and 410 F.; this fraction, which wascompletely paraillnic, amount to 80 per cent by weight of thetheoretical yield based on the formation of octane.

Example VI To a mixture of 438 cc. of 102 per cent sulfuric acid and 158grams of isopentane was added 89 grams of isopropyl chloride duringabout half an hour. The mixture was stirred vigorously during theaddition and for about half anvhour thereafter; the temperature of thereaction mixture was 68 F. The sulfuric acid was separated by settling,and the hydrocarbon layer was freed from acidic material by a causticalkali wash. After depentanization, the product contained over per centof hydrocarbons boiling in the gaso- ,line` range, almost 'half boilingin the octane range. The yield of gasoline was 37 per cent of thetheoretical yield of octane; this yield is relatively smaller than thoseobtained in the preceding examples because of the relatively short timeof reaction.

Example VII y A liquid'butane stream,`comprisingy isobutane as themajor'constituent, is mixed with about one-third an equivalent volume ofa 'material consisting principally bf isopropyl chloride. The resultantmixture or blend, is continuously and intimately. admixed, by amechanical mixing pump, with one-half the equivalent-volume of sulfuricacid having a strength of about 101 per cent, and consisting of a blen/dof equal parts of fresh andrecycled acid. The resultant liquid mixture,or emulsion, is rapidly lpassed through an elongated tube coil ofrestricted cross-sectional .area, which is immersed in a liquid bathwhich removes heat and maintains the reaction temperature below 80 F.The turbulence set up by the rapid flow through the tube coil aids inmaintaining an intimate mixture of the reactants. After a reaction timeof about 10 minutes, the stream is passed to separating means, whereinthe hydrocarbon material is separated from the sulfuric acid materialand from" hydrogen chloride. The free acid in the hydrocarbon materialisneutralized and removed/'by an alkali wash, and the stream is thenpassed to a series of fractionators. 'In these fractionators there isseparated a butane stream containing unreacted isobutane which isrecycled, Jan alkyl halide stream containing unreacted isopropylchloride which is also recycled, and ,a hydrocarbon fractionboilingwithin the motor-fuel range and containing a high concentrationof highly branched isoheptanes, such as 2,2,3-trimethylbutane and2,4-dimethylpentane, which have very good antiknock ratings. In order to'prevent an accumulation of undesirable constituents, a portion of thebutane stream and the alkyl halide stream may be removed from thesystem, or these streams may be subjected to further 'fractionation toproduce streams having higher concentrations of the desirableconstituents. The isoheptanes with high antiknock qualities are readilyseparated as a, hydrocarbon fraction having a narrow boiling range andcontaining them in high concentration.

In view of many possible modifications of the process that Will beobvious to those skilled in the art, the invention should not be limitedunduly by the foregoing specification and examples, but it should beunderstood to be as extensive in scope and equivalents as defined in theappended claims.

I claim: A

1. In a process for the production of paraffin hydrocarbons ofrelatively high molecular weight from parain hydrocarbons of lowermolecular weight, the steps which comprise establishing an intimateadmixture of an isoparaiiin in liquid phase, an alkyl halide in theliquid phase, selected from the group consisting of secondary andtertiary alkyl halides and having not more than six carbon atoms permolecule, and sulfuric acid having a strength greater than 90 per centby weight and containing between about 0.5 and per cent by weight ofaluminum sulfate as the catalyst, maintaining said intimate mixture at asuitable reaction temperature for a period of time sufiicient to effecta reaction of isoparafiin and alkyl halide to form isoparailns of highmolecular Weight, and subsequently separating from the reaction mixturea hydrocarbon fraction containing isoparafiins of high molecular weightso formed.

2. 'I'he process of claim 1 in which the alkyl halide is a tertiaryalkyl halide.

3. The process of claim l in which the alkyl halide is an alkylchloride.

4. The process of claim 1 in which the .alkyl halide is an alkylfluoride.

5. The process of claim 1 in which the alkyl halide ls a secondary alkylchloride and in which the strength of sulfuric acid is between 100 and105 per cent by weight.

6. The process of claim 1 in which the sulfuric acid has a strengthbetween 96 and 102 per cent by weight.

7. The process of claim l in which the sulfuric acid has admixed with ita portion of spent acid previously used in the process.

8. A process for the production of paramn hydrocarbons of relativelyhigh molecular weightv from parailln hydrocarbons of lower molecularweight, which comprises establishing an intimate admixture of anisoparailin having not more than eight carbon atoms per molecule, analkyl halide selected from the group consisting of secondary andtertiary alkyl halides and having not more than six carbon atoms permolecule, and sulfuric acid having a concentration greater than 95 percent by weight and containing between asiento 8 about 0.5 and 5 per centby weight of aluminum sulfate as the catalyst. maintaining said intimateadmixture at a reaction temperature not greater than about 125 F. foraperiod of time sumcient to effect reaction of alkyl halide withisoparaln to form an isoparaiiin of high molecular weight with elisionof the corresponding hydrogen halide. and subsequently removing from thereaction products a hydrocarbon fraction containing isoparafns of highmolecular weight so produced.

, 9. A process for the production of isoheptanesA having a highantiknock rating, which comprises establishing an intimate admixture ofisobutane, isopropyl chloride, and sulfuric acid having a concentrationgreater than 95 per cent by weight and containing between about 0.5 and5 per cent by Weight of aluminum sulfate as the catalyst,

maintaining said intimate admixture at a reaction temperature notgreater than about 125 F. for a period of time suillcient to effectreaction of isopropyl chloride with isobutane to form lsoheptanes witheli'sion of hydrogen chloride, and subsequently removing from thereaction products a hydrocarbon fraction containing isoheptanes soproduced.

10. A process for the production of isoparafiln hydrocarbons ofrelatively high molecular weight from isoparafiln hydrocarbons ofrelatively low molecular weight, which comprises establishing anintimate admlxture of an isoparaflin having not more than eight carbonatoms per molecule, an alkyl halide selected from the group consistingof secondary and tertiary alkyl'halides and having not more than sixcarbon atoms per molecule and sulfuric acid having a concentrationgreater than 95 per cent by weight and containing between about 0.5 and5 per cent by weight of aluminum sulfate as the catalyst, maintainingsaid intimate admixture ata temperature not greater than about 125 F.for a period of time sufficient to effect an alkylation reaction betweenalkyl halide and isoparaifln to form isoparafilns of higher molecularweight, subjecting the reaction eiliuent which comprises unreactedreactants, sulfuric acid and reaction products to a separating means toseparate sulfuric acid and hydrogen halide, passing at least a portionof said sulfuric acid to admixture with the incoming charge stock to thereactor, subjecting the remaining predominantly hydrocarbon portion ofthe reaction effluent to a treatment with alkali to remove acidicmaterial, passing alkali treated hydrocarbon reaction effluent tofractionating means to separate said eiliuent into a fraction containingisoparaflins in the motor fuel range and a light hydrocarbon fraction,recycling a portion of said light hydrocarbon fraction to saidalkylation reaction, and subsequently removing the fraction containingmotor-fuel range isoparaflins of higher molecular weight from theprocess.

l1. In a process of alkylating paramns to form lother paratllns ofhigher molecular weight, the

step which comprises inter-reacting an alkylatable parafiin hydrocarbonand an alkyl halide in the presence of concentrated sulfuric acidcontaining between about 0.5 and 5 per cent by weight of aluminumsulfate as the alkylating catalyst to form a paraiiin hydrocarbon ofhigher molecular weight.

FREDERICK E. FREY.

